---
title: BLS Signatures
---

Boneh–Lynn–Shacham (BLS) signatures form the foundation of [CometBLS](/architecture/cometbls).
They are cheaper to verify for both regular [IBC](/concepts/ibc) and zero-knowledge proof (ZKP) based IBC.
With BLS signatures, we can aggregate the public keys and the signatures and verify the aggregated signature with the aggregated public key.
BLS signature aggregation has a few advantages:

- Transaction size decreases compared to ECDSA verification. We do not need to transfer all signatures, just the aggregate.
- On-chain computation cost decreases. Instead of verifying each signature, we verify the aggregate.
- Zkp verification is much more efficient.
- State growth is significantly reduced.

Note that the Union validators do not produce zkps directly. This function is performed by [galois](/architecture/cometbls). Relayers can produce proofs or use Union as a distributed sequencing layer through proof claims.
